A well known constant velocity joint, used in the drive axles of front wheel drive motor vehicles, is the "Rzeppa" joint, described in U.S. Pat. No. 2,046,584, in which a driving member and a driven member transmit torque through a plurality (generally 6) of balls captured in longitudinal grooves in the driving and driven member and a cage. The geometry of the arrangement ensures that the balls are always aligned in a plane which bisects the angle between a pair of planes normal to the driving and driven axes of rotation; and constant velocity rotation of the driven member is thus assured, regardless of the joint angle between driving and driven members. As the joint angle increases, however, some portion of the driven member, usually the output shaft, eventually abuts some portion of the driving member to define a maximum joint angle. A variety of design factors and constraints work together to limit this maximum joint angle, and considerable effort has been expended in attempting to increase it. Such increases in maximum joint angle have generally come at the cost of an increase in joint package size, which is not desirable in the crowded engine compartments of front drive vehicles.
A modification of the original "Rzeppa" design is shown in U.S. Pat. No. 3,879,960 to Welschof et al. The constant velocity joint of this design is undercut-free: that is, the grooves of the outer joint member have a radial profile at the open end which is parallel to the joint axis so that they are not undercut in the longitudinal direction. The undercut-free design of this reference provides a reasonably high maximum joint angle; but an even higher joint angle is desired.